DOCSLIB.ORG

Airspeed Indicator Calibration

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Airspeed Indicator Calibration TECHNICAL GUIDANCE MATERIAL AIRSPEED INDICATOR CALIBRATION This document explains the process of calibration of the airspeed indicator to generate curves to convert indicated airspeed (IAS) to calibrated airspeed (CAS) and has been compiled as reference material only. i Technical Guidance Material BushCat NOSE-WHEEL AND TAIL-DRAGGER FITTED WITH ROTAX 912UL/ULS ENGINE APPROVED QRH PART NUMBER: BCTG-NT-001-000 AIRCRAFT TYPE: CHEETAH – BUSHCAT* DATE OF ISSUE: 18th JUNE 2018 *Refer to the POH for more information on aircraft type. ii For BushCat Nose Wheel and Tail Dragger LSA Issue Number: Date Published: Notable Changes: -001 18/09/2018 Original Section intentionally left blank. iii Table of Contents 1. BACKGROUND ..................................................................................................................... 1 2. DETERMINATION OF INSTRUMENT ERROR FOR YOUR ASI ................................................ 2 3. GENERATING THE IAS-CAS RELATIONSHIP FOR YOUR AIRCRAFT....................................... 5 4. CORRECT ALIGNMENT OF THE PITOT TUBE ....................................................................... 9 APPENDIX A – ASI INSTRUMENT ERROR SHEET ....................................................................... 11 Table of Figures Figure 1 Arrangement of instrument calibration system .......................................................... 3 Figure 2 IAS instrument error sample ........................................................................................ 7 Figure 3 Sample relationship between IAS and CAS for power off descent .............................. 8 Figure 4 Longitudinal alignment of pitot tube ........................................................................... 9 Figure 5 Vertical alignment of pitot tube ................................................................................ 10 Abbreviations and Symbols ASI: Airspeed Indicator CAS: Calibrated airspeed EFIS: Electronic Flight Information System IAS: Indicated airspeed ISA: International Standard Atmosphere Eins: Instrument error Epos: Position error Vqc: Simulated calibrated airspeed iv 1. BACKGROUND The aerodynamic forces acting on an aircraft are directly dependent on the dynamic pressure encountered by the aircraft. In essence, the dynamic pressure is that portion of the total pressure in the atmosphere that acts on the aircraft due to its movement through the air. The calibrated airspeed (CAS) is directly representative of the dynamic pressure acting on the aircraft regardless of altitude, wind, temperature etc. Thus, at a given CAS, the aerodynamic forces acting on the aircraft are constant, regardless of altitude, temperature etc. This conveniently means that the stall CAS for a given aircraft weight and configuration will be much the same within the flight envelope of a typical light aircraft, regardless of the environmental conditions. The pitot-static system installed in the aircraft attempts to display CAS to the pilot but is subject to numerous errors. In order to determine the relationship between indicated airspeed (IAS) and calibrated airspeed (CAS) it is necessary to account for the most significant errors present in the pitot- static system. These errors are instrument error and position error. • Instrument error: The error present in the reading of the instrument due to manufacturing imperfections and wear and tear. This can vary vastly depending on the make, age and condition of the instrument. • Position error: The error present in the reading due to the system sensing pressures that are not truly representative of what the aircraft is encountering. These errors come from the position on the aircraft at which the total and static pressures are sensed and can be affected by the pressure distribution around the aircraft, the propeller slipstream etc. Up to the time of writing, the standard pitot-static system installed in the Cheetah/BushCat made use of a pitot tube to sense total pressure, while the instruments themselves (ASI and altimeter) were left to sense static pressure within the cabin. This Technical Guidance Material aims to assist the owner/operator in generating the approximate relationships between IAS and CAS for their aircraft. Information is entered into the accompanying Excel spreadsheet and the calibration graphs will automatically be generated for your system. You can then print these graphs for reference. These relationships are subject to potential errors present in the tests used to obtain them, but 1 have been shown to be representative of reality (within about 1.5mph in their applicable range) when applied to another aircraft in the fleet. Note that if any changes have been made to the cabin, doors or pitot-tube of the aircraft, these will affect the validity of this method. 2. DETERMINATION OF INSTRUMENT ERROR FOR YOUR ASI The procedure to determine the instrument error present for your ASI is a relatively simple one but must be done carefully and accurately. It requires 2 people to accomplish and involves applying a pressure to the pitot tube to simulated a calibrated airspeed. This will generate a certain indicated airspeed on the instrument. This is done for multiple values all the way up and down the speed scale while recording the pressures corresponding to each indicated airspeed. Upscale and downscale readings are taken as, for example, the needle of the ASI may lag behind the movement of the pressure capsule due to mechanical free play in the linkages. This could mean that the indicated airspeed for a given calibrated airspeed in flight could vary depending on the movement of the linkages in the instrument before reaching that airspeed, and so it is important to determine the magnitude of this effect. Equipment: • Calibrated differential manometer. • Means to apply a pressure to the pitot tube (such as a small syringe). • Rubber/silicone tubing of roughly 4mm internal diameter. • T-piece connector to connect the syringe and manometer to the pitot tube. • Tie-wraps. Method: 1. Connect one end of the differential manometer to the t-piece connector using a length of rubber tubing. Secure a syringe to a free leg of the t-piece connector with another piece of rubber tube. 2. Zero the reading on the manometer. If there is no zeroing function, note the zero-IAS pressure reading as an entry in Column 1 for an IAS of zero. 2 3. Carefully attach the last end of the t-piece connector to the pitot tube itself with a third length of rubber tubing. When attaching the arrangement to the pitot tube, ensure that the plunger of the syringe is inserted and on its lower stop. Use tie-wraps to secure each connection. Figure 1 Arrangement of instrument calibration system 4. Have someone sit in the cabin viewing the ASI as the pilot would in flight. The second person must then slowly apply pressure to the syringe until the needle on the ASI reads the closest round value (usually about 20 to 25mph for analogue instruments). The person in the cabin calls when the desired value has been reached (record this in Column 1 of Appendix A, or the spreadsheet provided). 5. Hold the syringe steady (the friction on the plunger should be sufficient for you to let it go). Let the pressure value stabilise. i. Note that leaks will be evident by a steadily decreasing pressure value on the differential manometer. If the leak rate exceeds approximately 5-10 Pascals per second, it is likely that the pitot line itself has a leak and will have to be changed. ii. If the desired airspeed value on the ASI is overshot (for example, the needle indicates 22mph, rather than the desired 20), the pressure on 3 the system must be reduced to about 5mph below the intended value (15mph for the example given), before pressure is reapplied to obtain the correct value. 6. Record the reading on the differential manometer in Column 2of the sheet provided in the Appendix A. 7. Gradually apply pressure to the syringe to obtain the next speed value on the ASI and repeat the process. Go up in 5mph increments until at least 90mph. A 5ml syringe should be just sufficient to obtain the pressure required for this. 8. Once the highest speed has been obtained, gradually reduce pressure on the syringe until the next round number below it has been obtained. 9. Continue back down the speed scale taking pressure readings at the same values that you took going up the speed scale (completing Column 3, but from bottom to top). i. Note again that if the desired airspeed value on the ASI is overshot while reducing pressure (for example, the needle indicates 83mph, rather than the desired 85), the pressure on the system must be increased to about 5mph above the intended value (90mph for the example given), before pressure is slowly reduced again to obtain the correct value. ii. Once the applied pressure has been reduced to zero (plunger of syringe is completely removed from cylinder) note the zero reading on the manometer again in the zero IAS row. Section intentionally left blank. 4 3. GENERATING THE IAS-CAS RELATIONSHIP FOR YOUR AIRCRAFT Now that the pressure measurements are complete, Columns 1 to 3 of the sheet should be populated with values. This section details the calculation of Columns 4 to 19 in order to generate the relationship for your aircraft. This section requires some calculation and can be done manually with a pocket calculator, or using the spreadsheet provided. 1. Columns 4 and 5: Convert each measured upscale and downscale pressure to the CAS that it corresponds to (denoted as Vqc) using the formula below.
Load more

Recommended publications
  • Pitot-Static System Blockage Effects on Airspeed Indicator
    The Dramatic Effects of Pitot-Static System Blockages and Failures by Luiz Roberto Monteiro de Oliveira . Table of Contents I ‐ Introduction…………………………………………………………………………………………………………….1 II ‐ Pitot‐Static Instruments…………………………………………………………………………………………..3 III ‐ Blockage Scenarios – Description……………………………..…………………………………….…..…11 IV ‐ Examples of the Blockage Scenarios…………………..……………………………………………….…15 V ‐ Disclaimer………………………………………………………………………………………………………………50 VI ‐ References…………………………………………………………………………………………….…..……..……51 Please also review and understand the disclaimer found at the end of the article before applying the information contained herein. I - Introduction This article takes a comprehensive look into Pitot-static system blockages and failures. These typically affect the airspeed indicator (ASI), vertical speed indicator (VSI) and altimeter. They can also affect the autopilot auto-throttle and other equipment that relies on airspeed and altitude information. There have been several commercial flights, more recently Air France's flight 447, whose crash could have been due, in part, to Pitot-static system issues and pilot reaction. It is plausible that the pilot at the controls could have become confused with the erroneous instrument readings of the airspeed and have unknowingly flown the aircraft out of control resulting in the crash. The goal of this article is to help remove or reduce, through knowledge, the likelihood of at least this one link in the chain of problems that can lead to accidents. Table 1 below is provided to summarize
    [Show full text]
  • Sept. 12, 1950 W
    Sept. 12, 1950 W. ANGST 2,522,337 MACH METER Filed Dec. 9, 1944 2 Sheets-Sheet. INVENTOR. M/2 2.7aar alwg,57. A77OAMA). Sept. 12, 1950 W. ANGST 2,522,337 MACH METER Filed Dec. 9, 1944 2. Sheets-Sheet 2 N 2 2 %/ NYSASSESSN S2,222,W N N22N \ As I, mtRumaIII-m- III It's EARAs i RNSITIE, 2 72/ INVENTOR, M247 aeawosz. "/m2.ATTORNEY. Patented Sept. 12, 1950 2,522,337 UNITED STATES ; :PATENT OFFICE 2,522,337 MACH METER Walter Angst, Manhasset, N. Y., assignor to Square D Company, Detroit, Mich., a corpora tion of Michigan Application December 9, 1944, Serial No. 567,431 3 Claims. (Cl. 73-182). is 2 This invention relates to a Mach meter for air plurality of posts 8. Upon one of the posts 8 are craft for indicating the ratio of the true airspeed mounted a pair of serially connected aneroid cap of the craft to the speed of sound in the medium sules 9 and upon another of the posts 8 is in which the aircraft is traveling and the object mounted a diaphragm capsuler it. The aneroid of the invention is the provision of an instrument s: capsules 9 are sealed and the interior of the cas-l of this type for indicating the Mach number of an . ing is placed in communication with the static aircraft in fight. opening of a Pitot static tube through an opening The maximum safe Mach number of any air in the casing, not shown. The interior of the dia craft is the value of the ratio of true airspeed to phragm capsule is connected through the tub the speed of sound at which the laminar flow of ing 2 to the Pitot or pressure opening of the Pitot air over the wings fails and shock Waves are en static tube through the opening 3 in the back countered.
    [Show full text]
  • FAA Advisory Circular AC 91-74B
    U.S. Department Advisory of Transportation Federal Aviation Administration Circular Subject: Pilot Guide: Flight in Icing Conditions Date:10/8/15 AC No: 91-74B Initiated by: AFS-800 Change: This advisory circular (AC) contains updated and additional information for the pilots of airplanes under Title 14 of the Code of Federal Regulations (14 CFR) parts 91, 121, 125, and 135. The purpose of this AC is to provide pilots with a convenient reference guide on the principal factors related to flight in icing conditions and the location of additional information in related publications. As a result of these updates and consolidating of information, AC 91-74A, Pilot Guide: Flight in Icing Conditions, dated December 31, 2007, and AC 91-51A, Effect of Icing on Aircraft Control and Airplane Deice and Anti-Ice Systems, dated July 19, 1996, are cancelled. This AC does not authorize deviations from established company procedures or regulatory requirements. John Barbagallo Deputy Director, Flight Standards Service 10/8/15 AC 91-74B CONTENTS Paragraph Page CHAPTER 1. INTRODUCTION 1-1. Purpose ..............................................................................................................................1 1-2. Cancellation ......................................................................................................................1 1-3. Definitions.........................................................................................................................1 1-4. Discussion .........................................................................................................................6
    [Show full text]
  • 16.00 Introduction to Aerospace and Design Problem Set #3 AIRCRAFT
    16.00 Introduction to Aerospace and Design Problem Set #3 AIRCRAFT PERFORMANCE FLIGHT SIMULATION LAB Note: You may work with one partner while actually flying the flight simulator and collecting data. Your write-up must be done individually. You can do this problem set at home or using one of the simulator computers. There are only a few simulator computers in the lab area, so not leave this problem to the last minute. To save time, please read through this handout completely before coming to the lab to fly the simulator. Objectives At the end of this problem set, you should be able to: • Take off and fly basic maneuvers using the flight simulator, and describe the relationships between the control yoke and the control surface movements on the aircraft. • Describe pitch - airspeed - vertical speed relationships in gliding performance. • Explain the difference between indicated and true airspeed. • Record and plot airspeed and vertical speed data from steady-state flight conditions. • Derive lift and drag coefficients based on empirical aircraft performance data. Discussion In this lab exercise, you will use Microsoft Flight Simulator 2000/2002 to become more familiar with aircraft control and performance. Also, you will use the flight simulator to collect aircraft performance data just as it is done for a real aircraft. From your data you will be able to deduce performance parameters such as the parasite drag coefficient and L/D ratio. Aircraft performance depends on the interplay of several variables: airspeed, power setting from the engine, pitch angle, vertical speed, angle of attack, and flight path angle.
    [Show full text]
  • SERVICE ALERT Avidyne Primary Flight Display {P/Ns: 700-00006-000,-001,-002,-003,-100}
    SA-08-001 12 February 2008 SERVICE ALERT Avidyne Primary Flight Display {P/Ns: 700-00006-000,-001,-002,-003,-100} This SERVICE ALERT communicates important safety information concerning aircraft equipped with certain Avidyne EXP5000 Primary Flight Displays (PFDs). BACKGROUND INFORMATION Avidyne has received a limited number of field reports of PFDs displaying incorrect altitude and airspeed information. None of these occurrences led to an accident or incident. These occurrences included incorrect display of information at system startup, including one or more of the following: • Altitude significantly in error when compared to field elevation with local barometric correction setting entered on PFD. • Altitude significantly in error when compared to backup altimeter with identical barometric correction settings on both. • Non-zero airspeed (inconsistent with high winds or propwash from a nearby airplane) indicated at system startup. • Altitude or airspeed indications that vary noticeably after startup under static conditions. • Erroneous airspeed indications in combination with erroneous attitude indications. • A steady or intermittent “red X” in place of the airspeed indicator, altimeter, VSI or attitude indicator. Aircraft exhibiting any of these incorrect indications should not be flown. In any case where an erroneous indication is present at system startup (without an identifiable external cause such as surface winds or propwash) and this indication subsequently returns to normal, the PFD should nonetheless be considered unreliable and the aircraft should not be flown. As a normal practice, all pilots should be vigilant in conducting proper preflight and in- flight checks of instrument accuracy, including: • Preflight check of the accuracy of both the primary and backup altimeter against known airfield elevation and against each other.
    [Show full text]
  • FAHRZEUGTECHNIK Studiengang Flugzeugbau
    fachhochschule hamburg FACHBEREICH FAHRZEUGTECHNIK Studiengang Flugzeugbau Berliner Tor 5 D - 20099 Hamburg in Zusammenarbeit mit: University of Limerick Department of Mechanical & Aeronautical Engineering Limerick, Ireland Diplomarbeit - Flugzeugbau - Development of an aircraft performance model for the prediction of trip fuel and trip time for a generic twin engine jet transport aircraft Verfasser: Gerold Straubinger Abgabedatum: 15.03.00 Betreuer: Trevor Young, Lecturer 1. Prüfer: Prof. Dr.-Ing. Dieter Scholz, MSME 2. Prüfer: Prof. Dr.-Ing. Hans-Jürgen Flüh Fahrzeugtechnik Abstract This report gives an overview of methods for aircraft performance calculations. After explain- ing the necessary background and the International Standard Atmosphere, it deals with a com- plete mission of a generic twin engine jet transport aircraft, including the required reserves of a diversion. Every part of the mission is considered. This includes climb, cruise, descent and hold. Equations for determining significant parameters of all parts are derived and differences between idealized calculations (based on mathematical performance models) and real ones (based on aircraft flight test data) are explained. A computer program has been written as a macro in Lotus 1-2-3, with data obtained during flights. In the main report simple flowcharts are given to illustrate the methods used. The pro- gram results show the required fuel and the time for an airliner of a certain weight performing a mission with a certain range. In the appendix all data and the flowcharts
    [Show full text]
  • Introduction
    CHAPTER 1 Introduction "For some years I have been afflicted with the belief that flight is possible to man." Wilbur Wright, May 13, 1900 1.1 ATMOSPHERIC FLIGHT MECHANICS Atmospheric flight mechanics is a broad heading that encompasses three major disciplines; namely, performance, flight dynamics, and aeroelasticity. In the past each of these subjects was treated independently of the others. However, because of the structural flexibility of modern airplanes, the interplay among the disciplines no longer can be ignored. For example, if the flight loads cause significant structural deformation of the aircraft, one can expect changes in the airplane's aerodynamic and stability characteristics that will influence its performance and dynamic behavior. Airplane performance deals with the determination of performance character- istics such as range, endurance, rate of climb, and takeoff and landing distance as well as flight path optimization. To evaluate these performance characteristics, one normally treats the airplane as a point mass acted on by gravity, lift, drag, and thrust. The accuracy of the performance calculations depends on how accurately the lift, drag, and thrust can be determined. Flight dynamics is concerned with the motion of an airplane due to internally or externally generated disturbances. We particularly are interested in the vehicle's stability and control capabilities. To describe adequately the rigid-body motion of an airplane one needs to consider the complete equations of motion with six degrees of freedom. Again, this will require accurate estimates of the aerodynamic forces and moments acting on the airplane. The final subject included under the heading of atmospheric flight mechanics is aeroelasticity.
    [Show full text]
  • PILOTS GUIDE INTEGRATED STANDBY UNIT (ISU) with AUTOTHROTTLE (A/T) P/N: 9D-88126-1 (Legacy PC-12) P/N: 9D-88126-3 (PC-12 NG)
    Application Revisions Next Assy Used On Rev. Description Date Approved Approved 9K-88126-1 9K-88126-1 1 Initial Release per EC 14012 6/22/18 DB 9K-88126-3 9K-88126-3 2 Revised per EC 14069 7/24/18 DB 3 Revised per EC 14119 9/12/18 DB 4 Revised per EC 14128 9/21/18 DB 5 Revised per EC 14167 11/2/18 DB 6 Revised per EC 14167 11/20/18 DB PROPRIETARY THE RIGHTS OF INNOVATIVE SOLUTIONS & SUPPORT INC. ARE INCLUDED IN THE INFORMATION DISCLOSED HEREIN. THIS DRAWING AND/OR DOCUMENT SHALL NOT BE REPRODUCED OR TRANSFERRED TO OTHER DOCUMENTS OR USED OR DISCLOSED TO OTHERS FOR MANUFACTURING OR FOR ANY PURPOSE EXCEPT AS SPECIFICALLY AUTHORIZED IN WRITING BY INNOVATIVE SOLUTIONS & SUPPORT INC. PILOTS GUIDE INTEGRATED STANDBY UNIT (ISU) with AUTOTHROTTLE (A/T) P/N: 9D-88126-1 (Legacy PC-12) P/N: 9D-88126-3 (PC-12 NG) Contract Number: Contractor: Written By: M. Rudy Date: 6/21/18 PILOTS GUIDE Checker: Date: INTEGRATED STANDBY UNIT (ISU) Engineer: M. Rudy Date: 6/21/18 with AUTOTHROTTLE (A/T) Document Approval: D. Babe Date: 6/22/18 CAGE CODE QA Approval: B. Urbanski Date: 6/22/18 0EUW0 1D-13470 Design Approval: M. Knopf Date: 6/22/18 Form# 07315-372 Rev - SHEET 1 of 40 REVISION HISTORY Rev 6 Par 2.1: Modified to remove engine start mode with voltage monitoring and temperature protection. Removed Par 2.2 "Engine Start Mode" and all associated subparagraphs. Par 2.2: Changed from Par 2.3 and corrected spelling issue in header Par 2.2.1: Removed reference to engine start mode Rev 5 Added descriptions of Hot Start and Low Voltage Protection in Section 2.0.
    [Show full text]
  • Unusual Attitudes and the Aerodynamics of Maneuvering Flight Author’S Note to Flightlab Students
    Unusual Attitudes and the Aerodynamics of Maneuvering Flight Author’s Note to Flightlab Students The collection of documents assembled here, under the general title “Unusual Attitudes and the Aerodynamics of Maneuvering Flight,” covers a lot of ground. That’s because unusual-attitude training is the perfect occasion for aerodynamics training, and in turn depends on aerodynamics training for success. I don’t expect a pilot new to the subject to absorb everything here in one gulp. That’s not necessary; in fact, it would be beyond the call of duty for most—aspiring test pilots aside. But do give the contents a quick initial pass, if only to get the measure of what’s available and how it’s organized. Your flights will be more productive if you know where to go in the texts for additional background. Before we fly together, I suggest that you read the section called “Axes and Derivatives.” This will introduce you to the concept of the velocity vector and to the basic aircraft response modes. If you pick up a head of steam, go on to read “Two-Dimensional Aerodynamics.” This is mostly about how pressure patterns form over the surface of a wing during the generation of lift, and begins to suggest how changes in those patterns, visible to us through our wing tufts, affect control. If you catch any typos, or statements that you think are either unclear or simply preposterous, please let me know. Thanks. Bill Crawford ii Bill Crawford: WWW.FLIGHTLAB.NET Unusual Attitudes and the Aerodynamics of Maneuvering Flight © Flight Emergency & Advanced Maneuvers Training, Inc.
    [Show full text]
  • E230 Aircraft Systems
    E230 Aircraft Systems Fly fast Fly slow School Of 6th Presentation Engineering Air Speed Indicator • Airspeed indicator (ASI) is an instrument that measures speed relative to surrounding air. • The faster the aircraft the greater the dynamic air pressure. • ASI uses the difference in pitot and static pressure for measurement. • Compensation for variation in position, compression, density is necessary for true airspeed. • Shows indicated airspeed if uncorrected. School of Engineering Operation of ASI • Dy = Dynamic Pressure • S = Static Pressure • When aircraft is stationary, Dy = 0 • As pitot pressure increase, capsule expands to increase reading School of Engineering Markings on a ASI • White range: operating speed VS0 with flaps V S1 extended VNE • Green range: operating speed with flaps VFE retracted • Yellow range: May be operated in smooth air VN0 condition School of Engineering Markings on a ASI • VS0 – Stall speed with flaps/landing gear fully extended • VS1 – Stall speed with flaps/landing gear retracted • VFE – Maximum speed with flaps/landing gear fully extended • VN0 – Maximum speed with flaps/landing gear retracted • VNE – “Never Exceed” speed, beyond which structural damage may occur School of Engineering Airspeed conversion Corrected for Corrected for IAS position & CAS compressibility EAS instrument error effects Corrected for density Corrected for differences GS head/tail wind TAS • Memory aid: ICE-TG T G I C E School of Engineering Mach Number • Mach number = True Airspeed/Speed of sound • Speed of sound varies with temperature • Temperature varies with altitude • Thus Mach number varies with altitude • The same airspeed can have different Mach numbers depending on the flight altitude School of Engineering Machmeter • Knowing the airspeed alone is not enough to avoid shock waves forming at the critical Mach number • Pilot needs to know the Mach number and not the airspeed to avoid shock waves • That is why machmeter is needed.
    [Show full text]
  • G5 Electronic Flight Instrument Pilot's Guide for Certified Aircraft Blank Page SYSTEM OVERVIEW
    G5 Electronic Flight Instrument Pilot's Guide for Certified Aircraft Blank Page SYSTEM OVERVIEW FLIGHT INSTRUMENTS AFCS ADDITIONAL FEATURES INDEX Blank Page © 2017 Garmin Ltd. or its subsidiaries. All rights reserved. This manual reflects the operation of System Software version 5.00 or later. Some differences in operation may be observed when comparing the information in this manual to earlier or later software versions. Garmin International, Inc., 1200 East 151st Street, Olathe, Kansas 66062, U.S.A. Garmin AT, Inc.,2345 Turner Road SE, Salem, OR 97302, U.S.A. Garmin (Europe) Ltd., Liberty House, Hounsdown Business Park, Southampton, Hampshire SO40 9LR U.K. Garmin Corporation, No. 68, Zhangshu 2nd Road, Xizhi District, New Taipei City, Taiwan Web Site Address: www.garmin.com Except as expressly provided herein, no part of this manual may be reproduced, copied, transmitted, disseminated, downloaded or stored in any storage medium, for any purpose without the express written permission of Garmin. Garmin hereby grants permission to download a single copy of this manual and of any revision to this manual onto a hard drive or other electronic storage medium to be viewed for personal use, provided that such electronic or printed copy of this manual or revision must contain the complete text of this copyright notice and provided further that any unauthorized commercial distribution of this manual or any revision hereto is strictly prohibited. Garmin® is a registered trademark of Garmin Ltd. or its subsidiaries. This trademark may not be used without the express permission of Garmin. December, 2017 190-01112-12 Rev. A Printed in the U.S.A.
    [Show full text]
  • Air Data Computers
    TECHNOLOGY Air Data Computers BY KIM WIOLLAND PORTER-STRAIT INSTRUMENT CO. INC ir Data Computers have been The Beginning with us for many years now Initially, the main air data sensing A and have become increasingly application that concerned us was for more important, never more so then an altitude hold capability with the now as the RVSM mandate deadline autopilot. This “Altitude Capsule,” a approaches. The conventional aneroid simple aneroid just like an altimeter, pressure altimeter has been around is interfaced to a locking solenoid that for decades and is surprisingly accu- allows an error signal to be gener- Rockwell rate for a mechanical instrument. This Collinsʼ ated as the diaphragm changes with ADC-3000 instrument however will slowly lose altitude. All these capsules used gears, accuracy with increasing altitude. This cams, potentiometers and solenoids to eliminated these mechanical concerns. scale error is why they will not meet maintain a given altitude when com- Solid state pressure sensors and digital todayʼs stringent RVSM accuracy manded. In those days if the aircraft instruments are much more forgiving. requirements. The history of RVSM held within +/-100 feet, that was con- Current generation air data computers goes back further then you think, it sidered nominal, but then the accuracy have evolved into a separate sensor/ was first proposed in the mid–1950s would also vary at different altitudes. amplifier that provides a multitude of and again in 1973, and both times was These mechanically sensing instru- functions and information. rejected. With RVSM going into effect ments have at times been problems for The first generation of a Central Air this month, it will provide six new us all, failing to maintain proper pres- Data Computer (CADC) evolved out flight levels, increase airspace capac- sure rates on them during normal rou- of the Navy F14A Tomcat program in ity and most likely save hundreds of tine maintenance would cause undo the 1967-1969 time period.
    [Show full text]